1. Field of the Invention
The present invention relates generally to a pressure plate arrangement for a motor vehicle friction clutch with automatic wear compensation. The friction clutch can include a clutch housing, which clutch housing can be fastened to a flywheel that can turn around a clutch axis. The friction clutch can also further include a pressure plate, which pressure plate can be arranged in the clutch housing and which pressure plate can be displaced relative to the clutch housing in the direction of the clutch axis. Furthermore, the pressure plate can be supported at the flywheel by friction linings of a clutch disc. The friction clutch can still further include an energy storage device, preferably a membrane spring, which energy storage device can be supported with bias or pre-stress or pre-tension or pre-load between a contact area of the clutch housing and a contact area of the pressure plate. The friction clutch can additionally include a wear tolerance adjustment means with at least one wear compensation element to compensate for wear that occurs during operation, and an adjustment device to operate the wear compensation element.
The wear compensation element can include a ring element that can rotate around the clutch axis and has a toothed wheel work that can be arranged at least on the periphery of the ring element to compensate for wear. The adjustment device can include an axial advance element, which axial advance element can be positioned to rotate on a carrier around an axial advance element axis. The axial advance element can have, on an outer surface thereof, at least one axial advance segment, which at least one axial advance segment can act with the toothed wheel work on the ring element to Venerate an axial advance of the toothed wheel work of the ring element in the direction of the axial advance element axis. A one-way clutch can be assigned to the axial advance element, which clutch can allow for a rotation of the axial advance element in only one direction with respect to the carrier.
2. Background Information
U.S. Pat. No. 4,099,604 discloses a pressure plate arrangement for motor vehicle friction clutches wherein a membrane spring biases the pressure plate against the friction linings of a clutch disc. In a radial outer area, the membrane spring is supported by the clutch housing. Radially inside of the outer point of support, the membrane spring is supported by a wear compensation element. The wear compensation element is connected to and can rotate with the pressure plate through a thread around a clutch axis. By rotating the wear compensation element relative to the pressure plate, the axial extension of the unit formed by the pressure plate and the wear compensation element can be changed, and in particular can be increased, to compensate for wear play that occurs during operation. For this purpose, a worm or screw which combs or engages or threadingly meshes or threadingly engages with the inner circumference toothed wheel work of the wear compensation element is provided on a carrier on the pressure plate, which worm is connected to a lever through a one-way clutch. The lever and the worm are rotatably supported on the carrier, and the other end of the lever is positioned at the clutch release. The clutch release is coupled to the radial inner area of the membrane spring. The lever detects the wear and drives the worm during a subsequent release process through the one-way clutch; upon rotation of the worm, the wear compensation element that combs with the worm is turned around the clutch axis and thus compensates for the wear that has occurred.
In this known pressure plate arrangement, the wear is detected by the lever which is positioned on the one hand on the carrier attached to the pressure plate, and on the other hand on the clutch release which acts with the membrane spring in the radial inner area. However, when wear occurs, the pressure plate with the carrier and the lever positioned on said carrier move toward the clutch axis. Because the membrane spring is also supported by the pressure plate, it moves in its radial inner area, i.e., with the clutch release, also in the same direction as the pressure plate toward the clutch axis when the clutch is engaged. This means that the lever, which is supposed to detect the wear, detects the wear between two structural components which move in the same direction when wear occurs. Even a relatively high degree of wear thus leads to only an insignificant relative motion between the clutch release (which is coupled with the membrane spring) and the pressure plate.
U.S. Pat. No. 2,280,355 discloses a motor vehicle friction clutch wherein the wear compensation element is rotatably attached on the clutch housing by means of an outer thread. A multiple of arms or several arms or a plurality of arms which extend radially outward are provided on the clutch release sleeve. The radially outer areas of the arms bear on the pressure plate, while relative to the bearing point, the arms are positioned with contact radially inward at the wear compensation element. The wear compensation element is forced toward the arms by a coil or helical spring which acts between the clutch release sleeve and the wear compensation element and thus presses the arms against the pressure plate when the clutch is engaged. To compensate for wear that occurs during operation, the wear compensation element housing is rotatably attached to the clutch axis by a thread or threaded connection. An adjustment device includes a lever element connected to an adjustment toothed wheel work through a one-way clutch, and the lever element is positioned with contact on a radial inner segment of the clutch release. When wear occurs, the clutch release moves away from the pressure plate and thus leads to a displacement or swing or sweep of the lever element with respect to the toothed wheel work. In the subsequent clutch release process, the clutch release sleeve of this pressed clutch is pressed toward the pressure plate, whereby the lever element entrains the toothed wheel work through the one-way clutch, to then cause the wear compensation element to rotate around the clutch axis with a corresponding movement toward the pressure plate.
From a publication by Valeo Clutches, "Self Adjusting Technology in a Clutch" by Jacques Thirion de Briel, a pressure plate arrangement for a motor vehicle friction clutch is known wherein an adjustment device is attached to the membrane spring, which adjustment device effects the rotation of a wear compensation element around the clutch axis when wear occurs. To detect the wear, a first wear detection element which acts with a ratchet wheel arranged on the adjustment device is positioned with contact on the housing, while a second element, which second element also acts with the ratchet wheel, is positioned with contact on the membrane spring. When wear occurs, the membrane spring is displaced in axial direction relative to the housing, and the detection element positioned with contact on the housing moves correspondingly relative to the ratchet wheel. This leads to a torsion of the ratchet wheel, which is coupled with a worm. The worm combs or meshes or threadingly engages with teeth arranged at an outer circumference of the wear adjustment element, and causes the wear compensation element to rotate around the clutch axis and thus correspondingly adjusts the wear tolerance during a subsequent release of the clutch.
To detect the wear tolerance that occurs during operation, all of these known pressure plate arrangements for motor vehicle friction clutches require an assembly that is separate from the adjustment device, such as, for example, movably arranged levers, or detection elements which are affixed to or mounted on the housing and act with the corresponding wheels of an adjustment device. This requires an increased number of components in these known pressure plate arrangements, and a correspondingly higher assembling process.
Another pressure plate arrangement for a motor vehicle friction clutch with automatic wear compensation is known from German Patent Document DE-C 29 16 755, corresponding to U.S. Pat. No. 4,228,883, wherein the membrane spring engages in a radial outer area at a wear compensation element arranged on the pressure plate, and is supported in a more radially inward area on the housing. The wear compensation element is supported on the one hand by several slant surfaces arranged in the direction of the circumference on the wear compensation element, and on the other hand on the pressure plate by the pressure plate. An adjustment device is arranged on the housing radially outside the membrane spring and comprises a worm which combs with a toothed wheel work at the wear compensation element. The worm is coupled to an operation or actuating or control disc by a one-way clutch. The operation disc has on the periphery a notch where a radial outer segment of the membrane spring engages.
When wear occurs, the pressure plate and the wear compensation element move toward the pressure plate in the direction of the clutch axis, which leads to a sweeping motion or displacement of the membrane spring and a corresponding catch of the disk element. During the subsequent release of the clutch, the sweeping motion of the membrane spring leads in the opposite direction to catch the disk element, whereby the disk element is then non-rotationally coupled with the worm due to the one-way clutch and thus causes a rotation of the worm, which rotation is transferred to the wear adjustment element. The wear adjustment element then rotates relative to the pressure plate and thus adjusts the wear tolerance through the slant surfaces which act between the wear adjustment element and the pressure plate.
Because of the specific arrangement, this known pressure plate arrangement creates the problem that the membrane spring must be designed in such a manner that it extends to the radial outer area where the adjustment device and the disk element are arranged. This means that the membrane spring has a radial extension or span which corresponds to nearly the entire radial extension of the clutch housing. Thus, special membrane springs which can ensure sufficient pressure force of the pressure plate against the friction linings of the clutch disc even across such a great radial extension, are required for the production of a clutch of this type. In addition, a large volume area in the clutch housing cannot be used for other components because of the very great radial extension of the membrane spring.